Solvolysis of vinyl triflates. Effect of alkyl substituents, solvents, and added nucleophiles

Summerville, Richard H.; Senkler, C. A.; Schleyer, Paul von Ragué

doi:10.1021/ja00811a026

Cited by 55 publications

(23 citation statements)

References 3 publications

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“… 27 After screening of a variety of Brønsted bases (KO t Bu, NaOH) and solvents (DME, THF, 2,2,2-trifluoroethanol), no improvement in the yield of the ketone was found, and this strategy was abandoned. 28 …”

Section: Resultsmentioning

confidence: 99%

Total Synthesis of Alkaloid 205B

Tsukanov

Comins

2014

J. Org. Chem.

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Concise and highly stereocontrolled total syntheses of racemic and enantiopure frog alkaloid 205B (1) were accomplished in 11 steps from 4-methoxypyridines 6 and 7 in overall yields of 8 and 8%, respectively. The assembly of the core of the natural product relies on a stereoselective Tsuji–Trost allylic amination reaction and a ring-closing metathesis. The synthesis features the use of an N-acylpyridinium salt reaction to introduce the first stereocenter and an unprecedented trifluoroacetic anhydride-mediated addition of an allylstannane to a vinylogous amide with complete facial selectivity. Deoxygenation of the C4 ketone proved difficult but was accomplished via a modified Barton–McCombie reaction in the presence of a catalytic amount of diphenyl diselenide.

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Section: Resultsmentioning

confidence: 99%

Total Synthesis of Alkaloid 205B

Tsukanov

Comins

2014

J. Org. Chem.

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“…For all the polymers, the m/z values of major peak sets in MALDI-TOF exhibit integral multiple of molecular weight of the corresponding monomer unit, indicating that the major pathway of termination step is intramolecular abstraction of proton to give polymer with chain-end structure similar to D1. Meanwhile, minor peak sets were found in most of the MS spectra, which have a m/z value difference of 18 compared to the main peaks, relating to the hydrolysis of the triflate 47 terminal groups (similar to those in D2 and T1). After this process, carbonyl groups would be formed at the chain end, which is corroborated by the presence of a carbonyl vibration band in the FT-IR spectra as mentioned above (Figure 1a).…”

Section: ■ Introductionmentioning

confidence: 99%

“…The presence of the methylene group at one end of polymer chains is a strong evidence that the initiation of polymerization occurs through H + attacking at the alkynyl carbon adjacent to the TMS group. The other hydrogen atom of the methylene group is installed during the hydrolysis of the TMS group 47 either in situ or at the quenching step. The number-average MW (M n ) of the PPA1 was estimated to be around 4.7 kDa through GPC analysis.…”

Section: ■ Introductionmentioning

confidence: 99%

Silicon Promoted Cationic Polymerization of Phenylacetylenes

Zhao

Wang

et al. 2019

Macromolecules

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Poly(phenylacetylene)s (PPAs) are widely applied in a variety of research fields due to their good electrical and optical properties. Transition-metal-catalyzed polymerizations are generally performed for the synthesis of PPAs, while the residual metal catalysts might be problematic. In this work, we present a silicon promoted cationic polymerization of phenylacetylenes (PAs) by introducing a labile and electrondonating silyl group at the alkynyl termini of PA monomers. The polymerizations were performed in the presence of trifluoromethanesulfonic acid to rapidly produce the PPA products with good yields. The structures of the PPAs were characterized by NMR, IR, MALDI-TOF MS, UV−vis, and fluorescence spectroscopies, showing that the PPAs consist of conjugated skeletons with high contents of trans-configurations. GPC analysis showed a relatively narrow molecular weight distribution, and the molecular weight reached up to 4.7 kDa. A possible reaction scheme was proposed through further analysis on the structures of three kinds of oligomeric species. As the silyl groups are generally inherited from Sonogashira coupling reactions during the synthesis of PAs, this work presents a straightforward and metal-free method for the synthesis of PPAs.

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“…The (Z)-isomer, however, showed an increase in entropy of activation when a second CF 3 -group was present in the aromatic ring. At present, we do not know the source of this phenomenon, but ∆S ‡ for enol triflates varied according to substitution and solvent 15 and our numbers were determined over a somewhat narrow temperature range. The relative proportion of rearranged products in the current study is lower than in the previous study.…”

Section: Methodsmentioning

confidence: 97%

“…Isolation by kugelroehr distillation afforded the known isomers 15 which were dissolved and stored in pentane (GC MS, (Z)-and (E)-isomers with stereochemistry of isomers not determined, M + = 218).…”

Section: Preparation Of (E)-and (Z)-2-penten-3-yl Triflates (Methyl Mmentioning

confidence: 99%

Fragmentations of (E)- and (Z)- isomers of 2-methylbuten-1-yl(aryl)iodonium triflates: competing mechanisms for enol triflate formation

Hinkle¹,

Mikowski²

2003

Arkivoc

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We examined fragmentation reactions of (E)-and (Z)-2-methylbuten-1-yl(aryl)iodonium triflates (aryl = C 6 H 5 -, 4-(CF 3 )C 6 H 4 , 3,5-(CF 3 ) 2 C 6 H 4 -) to afford aryl idodides and six enol triflates. Four of these vinyl triflates involve alkyl migrations followed by triflate trapping of secondary vinyl cations whereas two do not involve migrations. Fragmentation rates in dry, neutral CDCl 3 were determined as were the distributions of enol triflate products. The ratios of rate constants for the (E)-/(Z)-isomers ranged between 5.0 and 8.5 and, in all salts, the rearranged enol triflate derived from migration of the alkyl moiety trans-to the aryliodonio-nucleofuge was observed in the greatest quantities. These data indicate that the fragmentation rates are significantly determined by the migratory aptitude of the trans-β-alkyl substituent and departure of the aryliodonionucleofuge occurs by anchimeric assistance. The ratios of inverted "unrearranged" enol triflate products were greater for the (Z)-isomers of the iodonium salt precursors indicating that steric effects play a role and implies that these inverted, unrearranged products are derived from inplane (σ*) S N 2 reaction. The presence of the remaining, retained, unrearranged enol triflate can be explained by a ligand coupling mechanism (π* S N 2) and the fragmentation mechanism(s) do not require the intermediacy of a primary vinyl cation.

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Solvolysis of vinyl triflates. Effect of alkyl substituents, solvents, and added nucleophiles

Cited by 55 publications

References 3 publications

Total Synthesis of Alkaloid 205B

Total Synthesis of Alkaloid 205B

Silicon Promoted Cationic Polymerization of Phenylacetylenes

Fragmentations of (E)- and (Z)- isomers of 2-methylbuten-1-yl(aryl)iodonium triflates: competing mechanisms for enol triflate formation

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